The National Transportation Safety Board determined that the probable cause of the accident was the pilots’ failure to follow established procedures and properly conduct a non-precision instrument approach at night in instrument meteorological conditions, including their descent below the minimum descent altitude before required visual cues were available (which continued un-moderated until the airplane struck the trees) and their failure to adhere to the established division of duties between the flying and non-flying (monitoring) pilot. The NTSB analysis of the Cockpit Voice Recorder suggests that both pilots were looking outside the cockpit for visual cues to the location of the airport and failed to realize how low they had descended below the glidepath.

Contributing to the accident were the pilots’ failure to make standard callouts and the current Federal Aviation Regulations that allow pilots to descend below the minimum descent altitude into a region in which safe obstacle clearance is not assured based upon seeing only the airport approach lights. The pilots’ failure to establish and maintain a professional demeanor during the flight and their fatigue likely contributed to their degraded performance.